Photodissociation dynamics of the thiolacetic acid at 243 nm with the velocity map ion imaging technique

Abstract

The MeCOS moiety of the thiolacetic acid (ethanethioic S-acid) is abundant and ubiquitous in the biological system. In special, it consists of one part of the Citric acid cycle which is a kind of the metabolism. If studies for its simplest form, MeCOSH make any progresses, the cornerstone for understanding the complex system, biological phenomena might as well be offered. Moreover, it used to be popular in organic syntheses. Apurba Bhattacharya et. al. reported its benign application in the synthesis of Acetaminophen™, which records the sales of c.a. $ 25,000,000 a year in the medicinal market. In other hands, as Kevin C. Sproull et. al. reported faster enzymatic transformations of thio acids, it is more reactive than oxygen analogs and has the properties different from oxygen analogs. But, though the sulfur compound, especially thiolacetic acid is a curious and interesting molecule, and has many applications to other regions and potentialities for enhancing human life, its physical and chemical properties has little been known. It is needless to say the photodissociation dynamics. In this work, we resolve the doublet from the SH group in the NMR data results from two conformational isomers of thiolacetic acid, cis and trans, based on theoretical work, density functional theory (B3LYP) and the $2^{nd}$ order Møller-Plesset perturbation theory. Also, we observed that the frontier orbitals (SOMOs) are aligned in the acyclic conjugated system as well as the cyclic conjugated system such as a thiophenol, Moreover, we report carefully in vacuo $D_0(MeCOS-D) = 86.574±0.217 kcal/mol$ for the trans conformer and in vacuo $D_0(MeCOS-H) = 82.954±0.141 kcal/mol$ for the cis conformer, and that two channels in the photodissociation of the thiolacetic acid at 243 nm would be probed: $MeCOSH → [MeCOS]``(\tilde{A},\tilde{X}) + H\mdot and MeCOSH → [MeCO]`` + [SH]``((_^2)Π_(1/2),(_^2)Π_(3/2))$. The transition dipole moment of the SH bond is aligned in perpendicular to ...